The present invention concerns a medical apparatus for placing embolization coils at selected sites within a patient""s cardiovascular system for treatment of cardiovascular diseases and vascular anomalies, such as aneurysms, arteriovenous fistulas and vascular shunts. In particular, the invention concerns a catheter system inducing embolization coils and an embolization coil placement device or xe2x80x9cpusherxe2x80x9d that uses a coil release assembly that is actuated by hydraulic pressure.
One of the current treatments for cardiovascular diseases and vascular anomalies, such as aneurysms, arteriovenous fistulas and vascular shunts, utilizes embolization coils which are introduced into the vascular anomaly to occlude it by creating a physical barrier to blood flow and encouraging thrombus formation. Typically, the embolization coils are placed at the desired location utilizing a microcatheter and an embolization coil placement device, often called a xe2x80x9cpusherxe2x80x9d. First, the site to be treated is catheterized with the microcatheter using flow directed techniques and/or with the aid of a steerable guidewire. Then, after removing the guidewire from the microcatheter, the embolization coil to be deposited is inserted and advanced through the microcatheter with the aid of the pusher. Once the end of the pusher has reached the distal end of the catheter, the embolization coil is pushed completely out of the microcatheter into the intended site. This technique of pushing the embolization coil out of the microcatheter poses a certain number of problems. Positioning the proximal end of the embolization coil cannot be performed with precision and, once the coil has begun to exit the catheter, it is impossible to reposition or to retrieve the embolization coil.
Several techniques have been proposed to permit more precise and controlled placement of embolization coils:
U.S. Pat. Nos. 5,122,136, 5,354,295, 5,540,680, 5,569,245 and 5,743,905 describe different variations of a system of embolization coil placement that uses electrical energy for releasing an embolization coil. The embolization coil is welded to a pusher wire that is used to maneuver the coil into the desired position. The embolization coil remains attached to the pusher wire even when it is pushed beyond the distal end of the microcatheter, which allows the embolization coil to be repositioned or retrieved, if necessary. Once the embolization coil is in the desired position, an electric current is passed through the welded area to electrolytically detach the embolization coil. The electrolytic detachment process is relatively slow, precluding the possibility of instantaneous release of the embolization coil. The electrolytic detachment process may also release deleterious chemical byproducts. In addition, the need for an electrical energy source adds to the cost and complexity of the embolization coil placement system.
U.S. Pat. No. 5,108,407 describes an embolization coil detachment system using light energy delivered through an optical fiber. The embolization coil is bonded to the pusher with a heat sensitive adhesive. When the embolization coil is in the desired position, laser energy is directed through the optical fiber to break the attachment. The laser ablation of the adhesive bond may possibly release undesirable chemical byproducts. In addition, the need for a laser energy source and an optical fiber adds significantly to the cost and complexity of the embolization coil placement system.
Other systems using mechanical embolization coil detachment mechanisms also exist, for example U.S. Pat. Nos. 5,304,195 and 5,261,916. In general, these mechanisms allow retraction of the coil as long as they have not completely exited the catheter, but they release the coil as soon as the pusher exits the distal end of the catheter.
U.S. Pat. Nos. 5,725,534 and 5,234,437 describe mechanical embolization coil detachment mechanisms utilizing a screw thread or a helical coil on the pusher that screws and unscrews from a threaded counterpart on the embolization coil. Proper operation of the coil detachment mechanism depends on precise engagement and disengagement of the threaded parts, which may not always be reliable under difficult clinical conditions.
U.S. Pat. Nos. 5,312,415 and 5,350,397 describe embolization coil placement systems that use a frictional attachment mechanism for controlling the release of the embolization coil. A pusher wire is used to release the embolization coil from the frictional attachment mechanism. The need for a precise interference fit for proper engagement of the frictional attachment mechanism adds significantly to the cost of the embolization coils and the delivery system.
Although these previous devices and systems represent, for the most part, a significant advance in the treatment of vascular disease, there continues to be a great need for improved systems of embolization coil placement that overcome the difficulties and inconveniences attendant with the existing systems.
In keeping with the foregoing discussion, the present invention provides a system for placement of embolization coils that is simple, reliable and easily achieved using known manufacturing techniques. The system includes an embolization coil and a pusher device for embolization coil placement. The embolization coil is typically constructed of a helically-wound wire coil of a biocompatible metallic alloy wire, or alternatively of a biocompatible polymer or a metal and polymer composite. Additionally, the embolization coil may include fibers or other thrombogenic materials. A releasable attachment assembly extends from the proximal end of the helically-wound wire coil. The releasable attachment assembly is preferably in the form of a deformable ring-shaped member connected to the helically-wound wire coil by an extension member. The ring-shaped member may be a simple annulus or it may have a convoluted or Z-shaped configuration.
The pusher device has a proximal tubular portion connected to a hydraulic pressure actuated coil release assembly. The hydraulic pressure actuated coil release assembly has an embolization coil mounting wire that extends distally from the proximal tubular portion. The mounting wire has a larger diameter distal portion that may be spherical, ellipsoidal, cylindrical or bulbous in shape. A small inflatable balloon member is mounted on the pusher device surrounding the embolization coil mounting wire and fluidly connected to the proximal tubular portion.
The embolization coil delivery system is prepared for use by mounting an embolization coil on the hydraulic pressure actuated coil release assembly by crimping the deformable ring-shaped member around the deflated balloon member and the mounting wire. The enlarged diameter of the distal portion of the mounting wire retains the crimped ring-shaped member on the hydraulic pressure actuated coil release assembly of the pusher device. The target site for the embolization coil is catheterized using a combination of microcatheters, flow directed catheters, guiding catheters and/or steerable guidewires. Then, the distal end of the pusher device with the embolization coil mounted on it is inserted into the microcatheter and advanced to the target site. The embolization coil can be advanced and withdrawn and manipulated as necessary to achieved optimum placement within the target site. Once the embolization coil is satisfactorily positioned, the inflatable balloon member is pressurized using a fluid-filled syringe or inflation device. As the inflatable balloon member expands, it deforms the ring-shaped member to release the embolization coil from the pusher device. The balloon member is then deflated and the pusher device is withdrawn. These steps may be repeated as many times as necessary to achieve satisfactory occlusion of the target site by creating a physical barrier to blood flow and encouraging thrombus formation.
The embolization coils and pusher device of the embolization coil placement system may be provided as components of a complete catheterization kit that may also include a combination of microcatheters, flow directed catheters, guiding catheters, steerable guidewires, a syringe or inflation device and instructions for use according to the methods described herein.
The many advantages of the embolization coil placement system of the present invention include: a completely controllable detachment assembly that does not depend on the position of the embolization coil and pusher assembly relative to the delivery catheter; a simple hydraulically actuated system of embolization coil detachment that is nonelectrical and nonmechanical and that does not require additional equipment, such as an electrical source or laser source; instantaneous detachment of the embolization coils; and no release of secondary products due to material ablation or chemical degradation. These and other advantages will be readily apparent to one of ordinary skill in the art upon reading the following detailed description of the invention taken in conjunction with the accompanying drawings.